The invention relates to a method for charging an electric vehicle and for air conditioning the vehicle interior.
In this context the term electric vehicle is understood to mean hereinafter not only the classical electric vehicles, but also electric vehicles with range extender as well as plug-in hybrid vehicles.
When an electric drive is used, the air conditioning of the vehicle interior—in particular, the cooling—can take place independently of operating the drive. Electric vehicles typically use an electric air conditioning system, which includes one or more electric powered consumers, for example an electric refrigerant compressor in the refrigerant circuit and/or an electric heater for heating the interior air. In contrast, the refrigerant compressor in conventional motor vehicles that are driven by an internal combustion engine are mechanically driven typically by way of the drive train; and a heat exchanger, which is heated by the heat of the cooling fluid, is used as the heater. It is also known from the prior art that motor vehicles that are driven by an internal combustion engine have stationary mode heating units; these stationary mode heating units are generally driven by burning the fuel contained in the tank.
The use of an electric air conditioning system makes it possible to provide stationary mode air conditioning functions independently of the operating state of the drive. For example, it can be provided that at the time of departure the vehicle has an air conditioning state that is comfortable for the vehicle user—in particular, a certain desired temperature—by suitably cooling (or heating).
In order to charge an electric vehicle, the vehicle is coupled to an electric energy supply by such means as a charging cable or by way of inductive coupling. If, on coupling the vehicle to an electric energy supply, the electric vehicle is not only charged, but also air conditioned in a parked position, then less energy is available for charging the electric vehicle when the electric grid power is limited (for example, 3.68 kW when charging at a standard socket having a single phase grid voltage of 230 V). With a limited charging time, the improved air conditioning may cause the state of charge to degrade at startup and, hence, result in a reduction in the cruising range of the electric vehicle. Although under some circumstances this drawback can be compensated by increasing the charging time, an increase in the charging time is often not possible given a respective time limitation. Pre-air conditioning the vehicle interior prior to departure not only improves the comfort of the vehicle user, but it also makes sense in terms of energy, because a subsequent activation of the air conditioning function after the departure is associated with a reduction in the cruising range. In that case then the limited energy from the electric energy accumulator of the electric vehicle has to be used for the air conditioning function.
Consequently, the demands for a high degree of air conditioning comfort, a long cruising range and a short charging time can be coordinated only with difficulty.
The object of the present invention is to provide a suitable method for charging the electric vehicle and for air conditioning the electric vehicle in stationary mode.
One aspect of the invention relates to a method for charging an electric vehicle with an electric energy accumulator and for stationary mode air conditioning the vehicle interior by use of an electric air conditioning system. In this case the vehicle is coupled to an electric energy supply by such means as a charging cable or by way of an inductive coupling, so that the electric energy can be received from the electric energy supply.
According to the method, the electric energy accumulator, for example a lithium ion battery, is charged to a minimum state of charge, for example a minimum SOC (state of charge) in the range between 40% and 70%, for example, 50%. After the energy accumulator has reached the minimum state of charge, the interior is air conditioned (for example, by cooling or heating) in such a way that at an assumed departure time a preset air conditioning state of the interior is reached. For example, a certain target temperature (for example, 22° C.) or a certain target temperature window (for example, 20° C. to 24° C.) is reached. However, this situation is possible only if there is still enough energy available between the time that the air conditioning is initiated and the time of departure to achieve this goal, for example when the time period prior to the assumed departure time is still adequately long.
The assumed departure time can have been manually entered, for example, by the vehicle user or can have been determined autonomously by the vehicle, for example, based on the vehicle itinerary history. For example, the next departure time can be estimated as a function of the current day of the week and/or the current time, because the vehicle knows from the itinerary history on which day of the week and/or at what time the vehicle is typically put into service.
The energy accumulator is charged to a target state of charge (for example, 97% SOC) with the excess energy that is not required to reach the desired air conditioning state, provided that excess energy is available. After reaching the minimum state of charge, the energy accumulator can be subsequently charged, for example, in parallel at the same time as the air conditioning.
According to the method, the charging measure is executed, for example, until the minimum state of charge. On reaching the minimum state of charge, a pre-air conditioning of the interior is executed immediately or later in such a way that a certain air conditioning state is reached at the time of departure. If there is still enough excess power available, the charging operation is continued, for example, in parallel. This does not necessarily mean that the pre-air conditioning starts immediately on reaching the minimum state of charge. The pre-air conditioning can also start at a later point-in-time (for example, 30 minutes prior to the assumed departure time), if it can still be achieved that the interior is adequately pre-air conditioned at the time of departure. On reaching the minimum state of charge, a pre-air conditioning of the interior is given priority over reaching the target state of charge in such a way that, for example, power for charging to the target state of charge may be used on such a scale prior and parallel to the pre-air conditioning, provided that complete pre-air conditioning can be ensured at the time of departure.
Therefore, in the event that both the charging time and charging power are limited, the method according to the invention enables a prioritization in such a way that the charging of the energy accumulator to a certain state of charge has a high priority. Lower priority is given to providing an air conditioning state at the time of departure, that is, the pre-air conditioning of the vehicle interior. However, the pre-air conditioning of the vehicle interior has higher priority than reaching a target state of charge for the energy accumulator.
The method according to the invention makes it possible to significantly improve the comfort by providing a desired air conditioning state at the time of departure. The improved comfort relates to both the high degree of comfort when boarding and also the comfort during the trip and is in general not just limited to the climate, but rather also relates to the acoustics (low noise level during the trip, because the pre-air conditioning allows the air conditioning system to run at a lower output during the trip). In contrast, when the charging time is limited and the grid power is low, a suitable choice of the minimum state of charge results in a cruising range that is only slightly reduced. In most cases a potential decrease in the absolute cruising range that is associated with the fulfillment of the air conditioning request and that is due to the possibly smaller charge cycle (charge cycle=difference between the state of charge at the time of departure and the state of charge at the start of charge) can be ignored and is noticeable—if at all—only when the energy accumulator is totally run down (however, it is seldom the case that the energy accumulator is totally run down). Therefore, the air conditioning of the interior can be guaranteed in essence independently of the surrounding conditions and the state of charge. Furthermore, in the event that the interior is pre-air conditioned, the cruising range is similar to or insignificantly less than the cruising range in the event that the interior is air conditioned exclusively after the vehicle startup.
Preferably on reaching the minimum state of charge it is checked whether the time period prior to the assumed departure time has reached or dropped below a defined time period threshold. In this case the air conditioning of the interior is started. For example, it is checked whether the time period prior to the departure time is less than Δt=30 minutes. The time period threshold is, for example, greater than or equal to the time period that is maximally required to achieve a preset air conditioning state under normal conditions. The time period threshold can be constant or variably adjustable, for example, as a function of the temperature prior to activating the air conditioning system, a target temperature for the time of departure and/or as a function of the available grid power (for example, 3.68 kW at a standard power supply or 19.2 kW at a high power supply).
It is advantageous, if while air conditioning the interior, the energy accumulator is charged at least intermittently in parallel with the excess energy that is not required to reach the air conditioning state. For example, both the interior can be air conditioned and the energy accumulator can be charged in a period directly preceding the time of departure. This strategy has the advantage that the time period, in which the basic power of the vehicle electrical system that is obtained independently of the actual air conditioning function and independently of the actual charge function, is reduced as compared to the situation, in which first the energy accumulator is charged and then only the air conditioning system runs without the energy accumulator being charged.
In certain situations it is advantageous to use the energy from the energy accumulator to air condition the interior, for example, when there is inadequate grid power. As a result, both the power from the electric energy supply and the power from the energy accumulator can be used simultaneously for air conditioning. For example, it can be checked whether the power made available by the energy supply for air conditioning the interior is adequate to reach the desired air conditioning state in the interior at the assumed departure time. For example, it can be checked whether the power of the energy supply is less than a required power value for the air conditioning. If this is the case, then stored energy is additionally retrieved from the energy accumulator for the air conditioning of the interior. When energy from the energy accumulator is used for pre-air conditioning, the state of charge can fall below the minimum state of charge under some circumstances.
This feature is especially advantageous under extreme outdoor conditions and low grid power and makes it possible to guarantee the desired air conditioning state at the start of a trip even in such cases.
The energy accumulator should not reach or exceed a certain temperature (for example, 32° C.), at which or rather above which the energy accumulator may run the risk of being, for example, damaged. In order to prevent such damage, the energy accumulator is typically cooled, in general also during the trip.
Preferably the energy accumulator is reduced to such a temperature at the assumed departure time that during an assumed trip (for example, at an average trip duration of 45 minutes), the cooling does not have to be activated, because an upper operating temperature limit, at which or above which the cooling of the energy accumulator would be activated, is not reached or not exceeded. The energy accumulator is reduced, for example, to such a temperature at the assumed departure time that at the assumed departure time plus an assumed temperature rise during the trip, the temperature remains below an upper operating temperature limit of the energy accumulator, or this upper operating temperature limit is not exceeded.
The pre-conditioning of the energy accumulator takes place prior to the assumed departure time preferably in such a manner that the temperature at the departure time is less than an upper operating temperature limit (for example, 32° C.), at which or above which the cooling of the energy accumulator would be activated, by at least 5° C., in particular by a value in the range of 7° to 22°.
For example, the same trip can always be assumed (for example, a trip of 45 minutes); as an alternative, a trip can be estimated based on the vehicle itinerary history.
The additional cooling of the energy accumulator makes it possible to avoid an energy consumption for cooling the high voltage accumulator during the assumed duration of the trip. This strategy makes it possible to extend in general the cruising range of the electric vehicle. If the trip lasts longer than assumed, then the energy consumption for the cooling is at least reduced.
Preferably the minimum state of charge or a related state of charge (for example, a lower state of charge, which lies below the minimum state of charge by a defined difference and which is not undershot even if the energy accumulator is discharged for pre-air conditioning purposes) is variably adjustable, for example, by way of a user input or by means of an automatic adjustment on the part of the vehicle. For example, the vehicle can evaluate the vehicle itinerary history and, in so doing, determine that, based on the past trips, a certain state of charge will basically suffice to complete the next trip. As an alternative or in addition, information about the upcoming trip can be derived by way of a look-ahead process. Then with this information about the upcoming trip a certain state of charge, which suffices for the upcoming trip, can be determined. For example, a destination can be entered by way of the navigation device in the vehicle (for example, when parking the vehicle); and a minimum state of charge or a related state of charge is adjusted as a function of this information. As an alternative, the next trip can be planned by specifying the destination by way of a data processing device that is located outside the vehicle, for example at home by means of a PC; and the minimum state of charge or a related state of charge can be adjusted as a function of this information.
The minimum state of charge can be decreased with respect to a specified value by individualization of the minimum state of charge—be it by way of a historical evaluation or look-ahead processes. The result of this approach is that at a given time and power for charging and pre-air conditioning, less time is required for charging to the minimum state of charge and that under some circumstances the air conditioning of the interior can start earlier, if desired.
Preferably it is provided that after the passage of the assumed departure time without a vehicle startup, the interior continues to be air conditioned for a certain run-on period (for example, for 30 minutes). This feature covers the not unusual situation, in which the driver reaches the vehicle somewhat later. As an alternative or in addition, the run-on time can be used to execute and/or complete one or more non-executed or incomplete measures for preparing the vehicle for the trip (for example, charging to a target state of charge or the pre-conditioning of the energy accumulator). Therefore, it is possible to catch up with the remaining extent of the charging, air conditioning and/or conditioning that was not fulfilled at the departure time during the run-on period.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.